I bought our 2002 LeSabre back in October and have put about 5000 miles on it. It has run sluggish ever since I bought it and had the classic catalytic converter rattle upon start-up.
Going up hills lately it has been really gutless and without power and fuel economy was getting terrible. Sometimes it would throw a P0420 code too.

Anyways today I got a new Magnaflow direct fit catalytic converter installed and my car runs like new now with lots of power and I hardly have to touch the gas pedal.

Needless to say I am really Hapy, pun intended.

DTC P0420 Catalyst System Low Efficiency! Sounds like the problem was detected & diagnosed correctly! Enjoy the new found power!